Our immediate goals are a detailed analysis of the radiation response and combined modality response (i.e., adriamycin and X-irradiation) of two established in vivo lines (Slow and S102F) of the C3H mouse mammary tumor. These analyses will be especially concerned with evaluating the therapeutic responses as they relate to the various growth kinetic parameters in the belief that such an approach will suggest a simplified model for optimizing protocols for fractionated radiation therapy and combined modality therapy. The single-dose TCD50/120's for the tumors under normal physiological conditions (i.e., mice breathing air) are 5508 plus or minus 282 and 3745 plus or minus rads respectively for the Slow and S102F tumors. Under hyperbaric oxygen conditions, the respective TCD 50/120's are 6374 plus or minus 514 and 3602 plus or minus 311 rads. If adriamycin is given first (10 mg/kg body wt.) followed by X-irradiation in two hours, the TCD50/120's are 5058 plus or minus 178 and 3419 plus or minus 198 rads respectively for the Slow and S102F tumors. Host toxicity was also determined by measuring the LD50/6 when whole-abdomen X-irradiation was administered at various times after the injection of adriamycin. The LD50/6 values for the various intervals between adriamycin injection and X-irradiation are: Control (X-ray only), 1214 plus or minus 48; 2 hrs, 1076 plus or minus 30; 12 hrs, 856 plus or minus 10; 2 days, 995 plus or minus 26; 3 days, 959 plus or minus 17; 5 days, 997 plus or minus 26, and 7 days, 1007 plus or minus 28 rads. BIBLIOGRAPHIC REFERENCES: Roti Roti, J.L., and Dethlefsen, L.A. Matrix Simulation of Duodenal Crypt Cell Kinetics, I. The Steady State. Cell Tissue Kinet. 8: 321-333, 1975. Roti Roti, J.L., and Dethlefsen, L.A. Matrix Simulation of Duodenal Crypt Cell Kinetics, II. Cell Kinetics following Hydroxyurea. Cell Tissue Kinet. 8:335-353, 1975.